[Blimp] Adds blimp engine browser test framework and LoadUrl test.

blimp/engine/app/blimp_content_main_delegate.cc

Index: blimp/engine/app/blimp_content_main_delegate.cc
diff --git a/blimp/engine/app/blimp_content_main_delegate.cc b/blimp/engine/app/blimp_content_main_delegate.cc
index 6e7b445ad4ca90bf93f68ddabc470db80543ed17..4e646ade8c898a1e7c4256b768ff528a0d3f3e4c 100644
--- a/blimp/engine/app/blimp_content_main_delegate.cc
+++ b/blimp/engine/app/blimp_content_main_delegate.cc
@@ -31,6 +31,9 @@ base::LazyInstance<BlimpEngineCrashReporterClient>
     g_blimp_engine_crash_reporter_client = LAZY_INSTANCE_INITIALIZER;
 
 namespace {
+
+BlimpContentMainDelegate* g_content_main_delegate = nullptr;
+
 void InitLogging() {
   // TODO(haibinlu): Remove this before release.
   // Enables a few verbose log by default.
@@ -54,9 +57,20 @@ void InitLogging() {
 }
 }  // namespace
 
-BlimpContentMainDelegate::BlimpContentMainDelegate() {}
+BlimpContentMainDelegate::BlimpContentMainDelegate() {
+  DCHECK(!g_content_main_delegate);
+  g_content_main_delegate = this;
+}
 
-BlimpContentMainDelegate::~BlimpContentMainDelegate() {}
+BlimpContentMainDelegate::~BlimpContentMainDelegate() {
+  DCHECK_EQ(this, g_content_main_delegate);
+  g_content_main_delegate = nullptr;
+}
+
+BlimpContentBrowserClient*
+BlimpContentMainDelegate::GetBlimpContentBrowserClient() {
+  return browser_client_.get();
+}
 
 bool BlimpContentMainDelegate::BasicStartupComplete(int* exit_code) {
   InitLogging();
@@ -77,6 +91,11 @@ void BlimpContentMainDelegate::PreSandboxStartup() {
   InitializeResourceBundle();
 }
 
+// static
+BlimpContentMainDelegate* BlimpContentMainDelegate::GetInstanceForTesting() {
+  return g_content_main_delegate;
+}
+
 void BlimpContentMainDelegate::InitializeResourceBundle() {
   base::FilePath pak_file;
   bool pak_file_valid = PathService::Get(base::DIR_MODULE, &pak_file);